For a baseline. On my 300+ HP V-8 ,I average about 11-14 degree difference between water out and water in temps... 30 degrees difference indicates you are not flowing the coolant at a proper speed. The coolant is spending too much time in the radiator, hence the big temp split.. My system holds 7 quarts and I circulate it about every 5 seconds. Worst split was when it was hot outside and I saw 11 degrees.  Best was 16 degrees and that was when it was -30f OAT.  Most aluminum blocks / aluminum rads  cooling systems are designed to to run in the 12 degree delta range. My experimental has been running that way for over 400 hours. IMHO.......

Ben Haas
www.haaspowerair.com